a) Field of the Invention
This invention relates to a tube-pressed brake suitable for use in a clutch, a brake or the like.
b) Description of the Related Art
Conventional tube-pressed brakes are each constructed of an outer frame, a tube arranged inside the outer frame, and a counterpart arranged inside the tube and rotatable relative to the tube. A pressure fluid is injected into the tube upon transmission of a torque, and is discharged upon allowing the brake to idle.
FIG. 5 is a cross-sectional view showing a conventional tube-pressed brake as viewed from a front, and FIG. 6 is a diagram illustrating an example of a fluid pressure circuit for the conventional tube-pressed brake. In these drawings, an outer frame 20, a pressure fluid supply hole 21, and a tube 30 are depicted. The tube 30 is folded back along opposite ends of the outer frame 20, between which a cut-off portion 23 is formed. The tube 30 is sealed and fixed at folded portions 31 thereof on the outer frame 20 by presser plates 40 and rivets 41, respectively.
Designated at numeral 32 are springs inserted within the tube 30. These springs 32 urge the tube 30 outwardly such that, during idling with the pressure fluid discharged from the tube 30, the tube 30 is prevented from contacting a brake drum (not shown) arranged inside the tube 30.
As is understood from the circuit diagram of FIG. 6, the pressure fluid is delivered by a pump 52 from a reservoir 53 to the pressure fluid supply hole 21 of the tube 30 via a solenoid-operated valve 60 through a line 50. Numeral 55 indicates a pressure control circuit which includes a relief valve 54. Upon transmission of a torque, the pressure fluid is delivered to the tube 30 via the solenoid-operated valve 60. Upon idling, on the other hand, the solenoid-operated valve 60 is changed over (into the position depicted in FIG. 6) such that the pressure fluid flows in an opposite direction through the line 50 and returns to the reservoir 53.
There is an important demand for providing clutch elements or brake elements with improved heat resistance and durability. A tube-pressed brake of the above-described conventional construction is unable to release heat produced during transmission of a torque, so that a friction surface of a tube and a counterpart, such as a drum, become hot. This leads to the occurrence of a problem in durability and also to the development of an inconvenience that the heat resistance has to be heightened.
To meet the above-described demand, the present invention provides a tube-pressed brake having a tube, said tube being inflatable by injection of a pressure fluid thereinto such that a torque can be transmitted to a counterpart, comprising a pressure fluid circuit for circulating said pressure fluid through an interior of said tube.
According to the present invention, the pressure fluid is allowed to circulate through the interior of the tube of the tube-pressed brake. This has made it possible to release heat, which is produced during transmission of a torque, to the outside of the brake. As a consequence, it has become possible to improve the durability of the tube and its counterpart, such as a drum, and hence to prolong their service life.